Process and Apparatus for the Preparation of a Cylinder Oil

ABSTRACT

The present invention concerns a process for the production of a cylinder oil comprising the steps: providing a used oil, providing a fresh cylinder oil, and blending the used oil with the fresh cylinder oil, wherein the used oil has a lower TBN value than the fresh cylinder oil. The invention further concerns a process for the operation of an internal combustion engine comprising the steps of: preparing a cylinder oil according to a process for the production of a cylinder oil as described herein and using the cylinder oil in the internal combustion engine. Also part of the present invention is an apparatus for the preparation of a cylinder oil, comprising a blending means for blending used oil and fresh cylinder oil, characterized in that the blending means is in flow communication with at least one compartment of an internal combustion engine that comprises used oil or at least one storage compartment comprising used oil, at least one storage compartment for fresh cylinder oil, and at least one cylinder of an internal combustion engine. A further aspect of the present invention is the use of used oil and fresh cylinder oil for the preparation of cylinder oil. The processes, apparatus and uses of the present invention are especially provided for the use with two-stroke crosshead engines installed on a ship.

INTRODUCTION

The present invention concerns a process for the production of acylinder oil comprising the steps:

-   -   providing a used oil,    -   providing a fresh cylinder oil, and    -   blending the used oil with the fresh cylinder oil,

wherein the used oil has a lower TBN value than the fresh cylinder oil.

The invention further concerns a process for the operation of aninternal combustion engine comprising the steps of:

-   -   preparing a cylinder oil according to a process for the        production of a cylinder oil as described herein, and    -   using the cylinder oil in the internal combustion engine.

Also part of the present invention is an apparatus for the preparationof a cylinder oil, comprising a blending means for blending used oil andfresh cylinder oil, characterized in that the blending means is in flowcommunication with

-   -   at least one compartment of an internal combustion engine that        comprises used oil or at least one storage compartment        comprising used oil,    -   at least one storage compartment for fresh cylinder oil, and    -   at least one cylinder of an internal combustion engine.

A further aspect of the present invention is the use of used oil andfresh cylinder oil for the preparation of cylinder oil.

The processes, apparatus and uses of the present invention areespecially provided for the use with two-stroke crosshead enginesinstalled on a ship and/or for four-stroke auxiliary engines installedon a ship.

PRIOR ART

Cylinder oil is an oil usually used for the lubrication of cylinders inan internal combustion engine. It has various functions. Its mainfunction is to provide lubrication between the cylinder and/or thepiston ring and cylinder liner. Its purpose is therefore wear control. Afurther important function is to prevent corrosion of the material ofthe cylinder and the material of the liner or walls of the combustionchamber. The cylinder oil itself should be stable against thermaldecomposition and it should have good antioxidant performance, goodantifoam performance and good water demulsability. Pressure performanceis also important for cylinder oils.

Most of these properties of cylinder oils are controlled by additives.The kinematic viscosity is mainly controlled by the components of theoil itself. Hydrocarbons with long carbon chains and hydrocarbons withbranched carbon chains tend to have higher kinematic viscosities.Corrosion prevention properties are induced into cylinder oils mainly byaddition of basic organic compounds, such as amines or the like. Organicdi-imines as described in GB 1,183,345 A are predominantly used incylinder oils as additive to control the corrosion preventionproperties. The basic additive neutralizes acids, e.g. sulfuric acid andother acids, that are formed during combustion in the combustion chamberfrom sulfur or sulfur containing compounds comprised in the fuel.Cylinder oil may comprise 0.1% to 30% by weight of these diimines. Afurther example for suitable anti-wear and anti-corrosion performanceenhancing additives are alkylamine-alkylphosphates as disclosed in US2004/144355 A.

For some lubricant applications such as in lubricating cylinders incrosshead diesel engines that employ all-loss lubrication systems andcombust heavy fuel oil with widely varying sulfur contents, the enginelubrication requirements vary to such a large degree and with sufficientfrequency that one lubricant formulation may not provide adequateperformance over the full range of operating conditions. This inabilitycan result in at least increased engine maintenance needs and moretypically unnecessary expense as a result of repair costs, down time andexcessive oil usage. Thus, there is a need for being able to vary thecomposition of a lubricant in response to an engine's actual lubricationrequirements. US 2004/144355 A suggests a system in which additives areadded to a primary lubricant in order to adapt the anti-corrosionproperties to the fuel and the engine conditions. The use of used oil isnot disclosed.

Cylinders usually have a larger amount of wear than other parts of theengine, have a higher temperature and the combustion process appliesfurther harsh conditions on cylinder oil. Cylinder oil is thereforeusually much more contaminated than oil in the rest of the engine(so-called system oil). In engines where the system oil is one and thesame with cylinder oil or is in contact with the cylinder oil, thecylinders introduce the major amount of pollutants into the system oil.In large engines that can use several tens of thousands of liters ofsystem oil, cylinder oil and system oil are therefore often separated inorder to protect the system oil from pollution. In such system, thecylinder oil cannot be regenerated by mixing with the system oil. Itsquality therefore deteriorates fast. In order to maintain a sufficientquality of the cylinder oil, it has to be exchanged often or it is usedonly in a once through operation in a so-called “all-loss” lubricatingsystem. In all-loss systems, cost for system oil is reduced but costsfor cylinder oil is still high. EP 1 640 442 B1 proposes a system wherespend system oil of an engine is mixed with additives to producecylinder oil. Such a system uses used oil to produce cylinder oil andtherefore reduces costs and environmental concerns. While this system ingeneral provides sufficient control of the corrosion properties of theproduced cylinder oil and makes the use of usual cylinder oil redundant,it also has disadvantages. The cylinder oil produced by this method hasa much lower kinematic viscosity and therefore inferior lubricationproperties than usual cylinder oil. Hence, it has to be used in largeramount to provide the same lubrication properties. Thereby the effect ofreduction of the oil consumption is diminished.

In addition, the additives used have a very high kinematic viscosity,often near 100 mm²/s at 100° C. or above. Such liquids can only be movedby pumps if the liquids are kept warm. Therefore, tanks, pipes, blenderand other equipment in contact with the additives need to be equippedwith heaters. In cold climate, also tankers and the like that carry theadditives to the ships or other installations in contact with theadditives need to be equipped with heater or need to be well isolated.Therefore logistic is a major problem when using such additives for theon-site manufacture of cylinder oil. Beyond the logistics there isalways the risk that local overheating that can easily occur andcontributes to oxidation of the additives and will reduce significantlythe quality of the additives and hence has an impact on the quality ofthe cylinder oil produced.

PROBLEMS TO BE SOLVED

It is the objective of this invention to provide a system that reducesthe amount of lubricants used in internal combustion engines, especiallythe amount of cylinder oil and/or system oil. At the same time, thepresent invention aims to provide a process and an apparatus thatprovides better control of the kinematic viscosity when producingcylinder oil from used oils. Improvement of wear and corrosion is afurther objective of the present invention.

DESCRIPTION OF THE PRESENT INVENTION

The present invention concerns a process for the production of acylinder oil comprising the steps:

-   -   providing a used oil,    -   providing a fresh cylinder oil, and    -   blending the used oil with the fresh cylinder oil,

wherein the used oil has a lower TBN value than the fresh cylinder oil.

This process allows the reuse of used oil as cylinder oil and thereforereduces cost and alleviates environmental concerns. It also provides atthe same time partially recycled cylinder oil with a higher kinematicviscosity than the processes described in the prior art, i.e. akinematic viscosity that is closer to the kinematic viscosity of usualcylinder oil. That blending of used oil and cylinder oil has suchadvantageous effects is surprising, especially for the blending ofsystem oil and cylinder oil, because the usual purpose of a cylinder oilcan only be obtained if system oil and cylinder oil are separated. Ithas therefore never been contemplated to blend these oils to produce acylinder oil prior to the invention.

According to the present invention cylinder oil is oil that is designedfor the use in the lubrication of a cylinder in an internal combustionengine. It preferably comprises basic, i.e. alkaline, additives.Preferably, the cylinder oil produced by the present invention is an oildesigned for the use as an all-loss oil. It is also preferred that thecylinder oil is designed for the use in crosshead diesel engines andespecially in two-stroke crosshead diesel engines, especially thoseinstalled on marine vessels, such as ships. The engines may, however,also be installed in a stationary system. Alternatively, it is preferredthat the cylinder oil is designed for the use in in four stroke dieselengines with or without crosshead, especially those installed on marinevessels, such as ships. Such engines could for example be auxiliaryengines on board of a ship for producing energy in conjunction with agenerator or the like.

It is further preferred that the used oil comprises at least in partused system oil from at least one crosshead diesel engine that employsan all-loss lubrication system for the cylinders. It is, however, mostpreferred that the internal combustion engine is installed on a ship andthat the process is performed on a ship. It is further preferred thatthe engine is a crosshead diesel engine that employs an all-losslubrication system for the cylinders.

In the context of the present invention the wording “fresh cylinder oil”denotes a cylinder oil that has no content of unprocessed used oil. Itmay, however, contain recycled oil that has been processed in a factory,i.e. recycling oil. Examples are usual commercially available cylinderoils. Preferably, the cylinder oils used in this invention have a highTBN value and a high viscosity. Especially useful is NAVIGO 100 MCL™with a kinematic viscosity of 20 mm²/s at 100° C. and a TBN value of 100(available from LUKOIL Marine Lubricants Ltd., Hamburg, Germany), whichis the only commercially available cylinder oil with a TBN value of 100or above.

In the context of the present invention, the wording “used oil” denotesan oil that has been used for lubrication of any kind or for otherpurposes or comprises such oil. It may have been used as such or it maycontain oils that have been used. Especially preferred is the use ofwaste oil that is otherwise disposed of.

One factor to be considered for the lubrication properties of cylinderoil is the kinematic viscosity. If the kinematic viscosity of thecylinder oil is too low, the oil film on the cylinder liner may not becontinuous and the cylinder or the piston ring may come in directcontact with the cylinder liner leading to increased wear. A furtherimportant factor for avoiding corrosive wear is the alkalinity reservein the oil film left on the cylinder surface. When the piston moves downthe cylinder surface is exposed to the aggressive atmosphere that causesthe corrosive wear. The oil film thickness left on the cylinder surfacedepends on the kinematic viscosity of the cylinder oil. The thinner thecylinder oil the lower the oil film thickness and the alkalinity reserveof the oil film covering the cylinder surface, as less oil comprisesless basic compounds per surface area, leading to higher level ofcorrosive wear. If the kinematic viscosity is too high, friction is toohigh, leading to loss of performance of the engine and in combinationwith a surplus in the alkalinity reserve it can form additional depositson the upper piston land and on the back of the piston ring leading tohigher wear levels or scuffing.

For the purposes of the present invention all values of the kinematicviscosity are measured according to DIN 51562/2. Accordingly, all valuesof kinematic viscosity stated herein are kinematic viscosities at 100°C. as described in DIN 51562/2.

The cylinder oil of the present invention preferably has a kinematicviscosity of 14 mm²/s or more at 100° C., more preferably of 15 mm²/s ormore at 100° C., even more preferably of 16 mm²/s or more at 100° C. andmost preferably of 17 mm²/s or more at 100° C. The fresh cylinder oil ofthe present invention preferably has a kinematic viscosity of 16 mm²/sor more at 100° C., preferably 18 mm²/s or more at 100° C. and mostpreferably of 19 mm²/s or more at 100° C. The kinematic viscosity of thefresh cylinder oil is preferably in a range of from 16 to 24 mm²/s at100° C., more preferably in a range of from 18 to 22 mm²/s at 100° C.and most preferably in a range of from 19 to 21 mm²/s at 100° C. Theused oil of the process of the present invention may have a kinematicviscosity of up to 25 mm²/s. The used oil of the process of the presentinvention preferably has a kinematic viscosity in the range of from 7 to15 mm²/s, more preferably of from 8 to 13 mm²/s, even more preferably offrom 9 to 12.5 mm²/s and most preferably of from 10 to 12.5 mm²/s.Preferred is a process as described herein, wherein the used oil has alower kinematic viscosity than the cylinder oil.

One parameter determining the corrosion prevention properties ofcylinder oils is the TBN value (also BN value or neutralization number).TBN is an abbreviation of “Total Base Number”, which defines thechemical equivalent of KOH in milligrams to the amount of an acidnecessary to neutralize the total base components included in 1 gram ofa sample. For the purposes described herein the TBN values aredetermined as described in ASTM D 2896.

The TBN value of the cylinder oil produced by any of the processes ofthe present invention is preferably adapted to the sulfur content of thefuel used in the internal combustion engine according to known methodsin the art. Background art in regard to this method is for exampledisclosed in US 2004/144355 A and references cited therein.

The cylinder oil produced by any of the processes described in thepresent application preferably has a TBN value of 10 or more, preferably30 or more, more preferably of 50 or more and most preferably of 60 ormore. The TBN value may also preferably be within one of the ranges 1 to80, 1 to 30, 1 to 25, 1 to 10, 10 to 80, 10 to 60, 10 to 30, or 30 to60. The used oil has typically a TBN value of 50 or less, more typicallyof 30 or less and usually of 15 or less. Preferably, the fresh cylinderoil used in this invention has a high TBN value and a high viscosity.Typically, the fresh cylinder oil used in the process of the presentinvention as described herein has a TBN value of 10 or more, preferablyof 50 or more, more preferably of 80 or more, even more preferably of 90or more and most preferably of 100 or more. It may also be preferable touse a fresh cylinder oil with a TBN value of 50 or less, of 40 or lessor of 25 or less.

Blending of the used oil and the fresh cylinder oil may be effected byany means know to the person skilled in the art to blend oils, preferredis however blending in a static mixing duct, blending pipe or in-lineblending unit. Useful static mixers that can be used for the presentinvention are for example described in U.S. Pat. No. 8,147,124.Alternatively, batch blending in a separate tank equipped with anagitator is also possible.

Preferred is further a process as described herein, wherein the used oilcomprises one or more oils selected from the group consisting of usedhydraulic fluids, used gear oils, used system oils, used trunk pistonengine oils, used turbine oils, used heavy duty diesel oils, usedcompressor oils and mixtures thereof. Preferably, the used oil comprisesused system oil. More preferably, the used oil consists of used systemoil.

The cylinder oil produced by any of the processes described hereincomprises typically at least 2% of used oil, preferably at least 5% ofused oil, and more preferably at least 10% of used oil. It is even morepreferred that the cylinder oil produced by any of the methods describedherein comprises at least 20% of used oil and most preferred at least30% of used oil. The cylinder oil produced by any of the processesdescribed herein may comprise at least 40% of used oil or at least 50%of used oil. Preferably, the cylinder oil produced by any of theprocesses described herein comprises at most 60% of used oil, morepreferably at most 50% of used oil, even more preferably at most 40% ofused oil and most preferred at most 30% of used oil. The amount of usedoil in the cylinder oil produced by any of the processes describedherein is preferably in a range of from 10% to 50%, more preferably offrom 20% to 40%.

The cylinder oil produced by any of the processes described hereincomprises typically at least 1% of fresh cylinder oil, preferably atleast 5% of fresh cylinder oil and more preferably at least 10% of freshcylinder oil. The cylinder oil produced by any of the processesdescribed herein may comprise at most 80% fresh cylinder oil or at least50% used oil. Preferably, the cylinder oil produced by any of theprocesses described herein comprises at most 80% fresh cylinder oil,more preferably at most 60% fresh cylinder oil, even more preferably atmost 40% fresh cylinder oil and most preferred at most 35% freshcylinder oil. In the cylinder oil produced by any of the processesdescribed herein, preferably the amount of used oil is at least 1%and/or the amount of fresh cylinder oil is at least 1%. More preferablythe amount of used oil is at least 1% and/or the amount of freshcylinder oil at least 5%. Even more preferably, the amount of used oilis at least 1% and/or the amount of fresh cylinder oil at least 10%.

Most preferably, the amount of used oil is at least 10% and/or theamount of fresh cylinder oil at least 10%. All amounts of used oil andfresh cylinder oil in the cylinder oil given herein are stated inpercent by weight, based on the total amount of the cylinder oilproduced in the process described herein, unless otherwise noted.

Also preferred is a process as described herein, especially as describedherein as preferred, wherein the used oil is obtained from an apparatuson a ship. Ships use oil in various apparatus in large amounts. Disposalof the used oil is costly. Costs of disposal may therefore be avoided ifthe used oil can be reused as cylinder oil. Further preferred is aprocess as described herein, wherein the process is performed on a ship.Disposal of used oil is only possible in harbors and cost for storagefacilities can be avoided if the used oil is directly consumed ascylinder oil without transport to a factory or the like, where cylinderoil could be produced from the used oil.

A further aspect of the present invention is a process for the operationof an internal combustion engine comprising the steps of:

-   -   preparing a cylinder oil according to any of the embodiments of        the process for the production of a cylinder oil as described        above, and    -   using the cylinder oil in the internal combustion engine.

Especially preferred is such a process where the internal combustionengine is a two-stroke crosshead engine. Further preferably, theinternal combustion engine of the process may be a four-stroke engine,in particular an auxiliary engine installed on a ship.

Further preferred is such a process, wherein

-   -   the internal combustion engine is a two-stroke crosshead engine        or a four-stroke engine,    -   the cylinder oil is used as an all-loss cylinder oil, and    -   the used oil comprises used system oil of the two-stroke        crosshead engine or of the four-stroke engine respectively. In        such a process, the used system oil of the two-stroke crosshead        engine or of the four-stroke engine respectively may be used        completely for the preparation of the cylinder oil according to        the process of the present invention and costs for storage and        disposal can be saved. The cylinder oil produced in such a        process can be exactly adjusted for the TBN values needed for        the fuel used and the viscosity of the cylinder oil produced is        close to that of fresh cylinder oil. Further preferred are any        of the processes for the operation of an internal combustion        engine as described herein, wherein the two-stroke crosshead        engine and/or the four-stroke engine respectively is installed        on a ship.

Preferred is also any one of the processes for the operation of aninternal combustion engine as described herein, wherein

-   -   the used oil is derived from at least one engine compartment or        at least one storage compartment,    -   the used oil is blended with the fresh cylinder oil by means of        a blending means, and    -   the cylinder oil is delivered to at least one cylinder of the        internal combustion engine.

The used oil, the fresh cylinder oil and the cylinder oil of thisprocess may be of any kind as described herein. In such a process theusual equipment used with an internal combustion engine, e.g. the oilsump and the cylinders are preferably connected to the blending means.Conventional internal combustion engines can therefore easily beretrofitted with this system without large expenses and with minimaladditional equipment, i.e. piping, a blender and maybe pumps.

Further preferred is any one of the processes for the operation of aninternal combustion engine as described herein, wherein the amount ofused oil and cylinder oil blended is determined by the TBN value desiredfor the cylinder oil, the TBN value of the used oil and the TBN value ofthe fresh cylinder oil. This allows production of cylinder oil with anexactly determined TBN value and therefore its adjustment to the fuelused.

A further aspect of the present invention is an apparatus for thepreparation of a cylinder oil, comprising a blending means for blendingused oil and fresh cylinder oil, characterized in that the blendingmeans is in flow communication with

-   -   at least one compartment of an internal combustion engine        designed to comprise used oil or at least one storage        compartment designed for used oil,    -   at least one storage compartment for fresh cylinder oil, and    -   at least one cylinder of an internal combustion engine.

A compartment of an internal combustion engine designed to comprise usedoil is a compartment of the internal combustion engine that in usualoperation of the engine comprises used oil or may comprise used oil andcan be used for the removal of used oil. A storage compartment for freshcylinder oil is any storage compartment that can hold cylinder oil.Again, this apparatus makes full use of the equipment usually installedat an internal combustion engine that uses cylinder oil, for example,the oil sump or a compartment of the internal combustion engine and thestorage tank for the fresh cylinder oil. Only a blending means, pipingand possibly pumps have to be installed to prepare a usual installationfor the operation of an internal combustion engine for the use with theprocess as described herein. The piping and tanks usually need noadditional heating or equipment of any other kind.

Further preferred is an apparatus as described herein, comprisingadditionally

-   -   a pump for the transport of used oil to the blending means,    -   a pump for the transport of the fresh cylinder oil to the        blending means, and    -   at least one storage compartment for the prepared cylinder oil.

Also preferred is an apparatus as described herein, wherein the used oilcomprises used system oil of the internal combustion engine. Asdescribed above, for the equivalent process, this apparatus allows theoptimal use of the used system oil and the production of a cylinder oilthat has exactly the required TBN-value and a kinematic viscosity thatis closer to the desired value than that of the processes of the priorart. Most preferred is an apparatus as described herein, wherein theinternal combustion engine is a two-stroke crosshead engine or afour-stroke engine, in particular a four-stroke auxiliary engineinstalled on a ship.

The apparatus according to the present invention may compriseadditionally a system oil tank, which is connected by piping to theblending means. This allows the use of fresh system oil instead of or inaddition to the used system oil.

A further aspect of the present invention is a ship comprising anapparatus as described herein.

A further aspect of the present invention is the use of used oil andfresh cylinder oil for the preparation of cylinder oil. The used oil andthe fresh cylinder oil of the inventive use as well as the cylinder oilthat results from the inventive use may be of any kind described herein.

The processes, apparatus and uses of the present invention areespecially provided for the use with reciprocating internal combustionengines and most preferably with two-stroke crosshead engines and/orwith four-stroke (auxiliary) engines. Most preferably, the engines areinstalled on a ship.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: FIG. 1 describes an example for an apparatus of the presentinvention.

FIG. 2: FIG. 2 describes another example for an apparatus of the presentinvention.

FIG. 3: The graph of FIG. 3 shows the TBN value as a function of theamount of system oil in the cylinder oil prepared according to thepresent invention (Graph B) and according to the method described in EP1 640 442 B1 (Graph A).

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an internal combustion engine 1 with an oil sump 2, whichis connected via piping 3 with blending means 5. It further shows afresh cylinder storage tank 6 connected via piping 7 with the blendingmeans 5. The blending means is further connected via piping 9 to thecylinder oil injection openings in the cylinder 10 of internalcombustion engine 1. Pipings 3, 7 and 9 each comprise a valve 4 andpiping 9 further comprises a pump 8. The valves 4 and the pump 8 areconnected to a controller 11.

In usual operation mode, the TBN value of the cylinder oil produced bythe blending means 5 and flowing into piping 9 is measured by aninstrument known in the art (not shown) and an electrical signal issubmitted to the controller 11. The controller 11 uses the signal todetermine the amount of system oil from the oil sump 2 and the amount offresh cylinder oil from the fresh cylinder storage tank 6 that areneeded to produce the cylinder oil with the TBN value required. Thecontroller 11 controls the valves 4 and the pump 8 in order to providethe correct amount of cylinder oil with the correct TBN value to the oilinjection openings in the cylinder 10 of internal combustion engine 1.For the case that a cylinder oil with very high TBN value is requiredfor the operation of the internal combustion engine 1, controller 11 canbe programed such that 100% fresh cylinder oil is provided to thecylinder oil injection openings in the cylinder 10 of internalcombustion engine 1.

FIG. 2 depicts a similar embodiment of the present invention as FIG. 1.The embodiment of FIG. 2 has additionally a system oil tank 12, which isconnected by piping 14, which comprises a further valve 4, to theblending means 5. This allows the use of fresh system oil instead or inaddition to the used system oil from oil sump 2. The apparatus may alsobe fitted with additional piping and valves that would allow thecontroller 11 to replenish the system oil used or removed from oil sump2. FIG. 2 further shows a cylinder oil tank 13 that can be used tobuffer cylinder oil production and use.

EXAMPLE

The following example will show the advantages of the present inventionin view of the prior art for a typical example of a cylinder oil. Table1 shows for the commercially relevant TBN values 40 to 100 the amount ofsystem oil that must be blended with the additives or with freshcylinder oil, respectively, to arrive at the desired TBN value. Column 3of table 1 concerning the additives is calculated in accordance with thesystem known from EP 1 640 442 B1. As fresh cylinder oil, NAVIGO 100MCL™ (available from LUKOIL Marine Lubricants Ltd., Hamburg, Germany)with a kinematic viscosity of 20 mm²/s at 100° C. and a TBN value of 100has been used. As system oil a commercially available system oil with aTBN value of 6 and a kinematic viscosity of 11.5 mm²/s at 100° C. hasbeen used (i.e. NAVIGO 6 SO). As additive, a commercially availableadditive (i.e. Chevron OLOA 49805) with a TBN value of 320 and anapparent kinematic viscosity of 39 has been used. The measured kinematicviscosity of the additives is 101 mm²/s at 100° C. However, theadditives are non-Newtonian fluids and the flow properties differ fromthose of Newtonian fluids when diluted with oils. In mixtures withsystem oil, the additive behaves as if it has a kinematic viscosity of39 mm²/s at 100° C. The later value is therefore used for thecalculation of the kinematic viscosity of the resulting cylinder oil.

The TBN value of the resulting cylinder oil is the weighted mean averagevalues of the TBN values of the system oil and the fresh cylinder oilused. The values of the amount of system oil necessary to reach thedesired TBN value has been calculated accordingly.

TABLE 1 TBN values of Mixtures of system oil with fresh cylinder oil oradditives Fresh cylinder oil Additives Weight percent system Weightpercent system TBN oil in the mixture oil in the mixture 40 63.83%89.17% 50 53.19% 85.99% 60 42.55% 82.80% 70 31.91% 79.62% 80 21.28%76.43% 90 10.64% 73.25% 100 00.00% 70.06%

FIG. 3 shows the same data as Table 1 as in the form of graphs, i.e. theTBN value as a function of the amount of system oil in the resultingcylinder oil. As can be seen, for any of the commercially useful TBNvalues, an amount of at least 70% system oil is necessary to arrive atthe desired TBN value, if the cylinder oil is produced according to theprior art (Graph A). In contrast, according to the present invention(Graph B), an amount of 0% to about 64% system oil is necessary. For aMAN B&W two-stroke crosshead engine with a bore of 80 cm, when using aheavy fuel oil (HFO) with a sulfur content of 3% by weight, a cylinderoil with a TBN value of 70 and a kinematic viscosity of 17 isrecommended at a feed rate of 0.6 g/kWh. For the desired TBN value of70, about 30% cylinder oil is necessary according to the presentinvention and about 80% according to the prior art. For such an engine,the manufacturer recommends the continued renewal of a certain amount ofsystem oil used in the engine in order to replenish the system oil andto remove used system oil. The use of about 30% of system oil in thecylinder oil would be in accordance with the amount of used system oilthat needs to be withdrawn from the engine continuously. Therefore, theprocess according to the present invention uses about the same amount ofused system oil that accumulates in the same time from the oil exchangein the engine. In contrast, the process according to EP 1 640 442 B1uses more than twice that amount, resulting in the use of system oilthat is almost unused, thereby resulting in waste.

As discussed, for the above-mentioned engine, a heavy fuel oilcomprising 3% by weight sulfur, a TBN value of 70 and a viscosity of 17are recommended. From the amount of system oil and fresh cylinder oil inthe resulting cylinder oil and the viscosity data of the system oil andthe fresh cylinder oil, the kinematic viscosity of the resultingcylinder oil can be calculated according to the equation ofUbbelohde-Walther (see DIN 51563). For the mixtures with a TBN value of70, the viscosities are significantly lower than the recommendedviscosity, namely 14.3 mm²/s at 100° C. for a mixture of system oil andadditives and 16.6 mm²/s at 100° C. for a mixture of system oil withfresh cylinder oil. As can be seen, the cylinder oil produced accordingto the present invention has a kinematic viscosity that is almostidentical to the target viscosity, i.e. 16.6 mm²/s at 100° C. ascompared to the desired 17 mm²/s at 100° C. In contrast, the kinematicviscosity of the cylinder oil produced according to the prior art has aviscosity that is much lower than the target viscosity, i.e. 14.3 mm²/sat 100° C. as compared to 17 mm²/s at 100° C.

As discussed above, because the viscosity of the oil film is too low forthe cylinder oil prepared according to the prior art, the oil film onthe cylinder liner may not be continuous and the cylinder or the pistonring may come in direct contact with the cylinder liner leading toincreased wear. Furthermore, as a consequence of the low oil filmthickness the alkalinity reserve of the oil film covering the linersurface is too low, as less oil comprises less base compounds persurface area (which leads to a reduced alkalinity reserve), leading to ahigher level of corrosive wear. This also results in a reducedalkalinity reserve. As a consequence, the feed rate for the cylinder oilhas to be higher for the cylinder oil prepared according to the priorart. The present invention therefore reduces wear, corrosion and theamount of cylinder oil used and is therefore advantageous in theoperation of internal combustion engines over the prior art.

LIST OF REFERENCE NUMERALS

1 internal combustion engine

2 oil sump

3 piping

4 valve

5 blending means

6 fresh cylinder storage tank

7 piping

8 pump

9 piping

10 cylinder of internal combustion engine

11 controller

12 system oil tank

13 cylinder oil tank

14 piping

1. Process for the production of a cylinder oil comprising the steps:providing a used oil, providing a fresh cylinder oil, and blending theused oil with the fresh cylinder oil, wherein the used oil has a lowerTBN value than the fresh cylinder oil.
 2. Process according to claim 1,wherein the cylinder oil produced comprises at least 1% by weight usedoil, based on the total amount of cylinder oil produced and/or at least1% by weight of fresh cylinder oil, based on the total amount ofcylinder oil produced.
 3. Process according to claim 1, wherein thecylinder oil produced comprises at least 10% by weight used oil, basedon the total amount of cylinder oil produced and/or at least 10% byweight of fresh cylinder oil, based on the total amount of cylinder oilproduced.
 4. Process according to claim 1, wherein the used oil has alower kinematic viscosity than the cylinder oil.
 5. Process according toclaim 1, wherein the used oil comprises one or more oils selected fromthe group consisting of used hydraulic fluids, used gear oils, usedsystem oils, used trunk piston engine oils, used turbine oils, usedheavy duty diesel oils, used compressor oils and mixtures thereof. 6.Process according to claim 1, wherein the process is performed on amarine vessel.
 7. Process for the operation of an internal combustionengine comprising the steps of: preparing a cylinder oil using a processfor the production of a cylinder oil, said process for the production ofa cylinder oil comprising the steps: providing a used oil, providing afresh cylinder oil, and blending the used oil with the fresh cylinderoil, wherein the used oil has a lower TBN value than the fresh cylinderoil, and using the cylinder oil in the internal combustion engine. 8.Process according to claim 7, wherein the internal combustion engine isa two-stroke crosshead engine, the cylinder oil is used as an all-losscylinder oil, and the used oil comprises used system oil of thetwo-stroke crosshead engine.
 9. Process according to claim 7, whereinthe used oil is derived from at least one engine compartment or at leastone storage compartment, the used oil is blended with the fresh cylinderoil by means of a blending means, and the cylinder oil is delivered toat least one cylinder of the internal combustion engine.
 10. Processaccording to claim 7, wherein the amount of used oil and cylinder oilblended is determined by the TBN value desired for the cylinder oil, theTBN value of the used oil and the TBN value of the fresh cylinder oil.11. Apparatus for the preparation of a cylinder oil, comprising ablending means for blending used oil and fresh cylinder oil, wherein theblending means is in flow communication with at least one compartment ofan internal combustion engine that comprises used oil or at least onestorage compartment comprising used oil, at least one storagecompartment for fresh cylinder oil, and at least one cylinder of aninternal combustion engine.
 12. Apparatus according to claim 11,comprising additionally a pump for the transport of used oil to theblending means, a pump for the transport of the fresh cylinder oil tothe blending means, and at least one storage compartment for theprepared cylinder oil.
 13. Apparatus according to claim 11, wherein theinternal combustion engine is a two-stroke crosshead engine.
 14. Shipcomprising an apparatus for the preparation of a cylinder oil,comprising a blending means for blending used oil and fresh cylinderoil, wherein the blending means is in flow communication with at leastone compartment of an internal combustion engine that comprises used oilor at least one storage compartment comprising used oil, at least onestorage compartment for fresh cylinder oil, and at least one cylinder ofan internal combustion engine.
 15. (canceled)
 16. Process according toclaim 1, wherein the amount of used oil and cylinder oil blended isdetermined by the TBN value desired for the cylinder oil, the TBN valueof the used oil and the TBN value of the fresh cylinder oil.
 17. Processaccording to claim 1, wherein the fresh cylinder oil has a TBN value of50 or more.
 18. Process according to claim 1, wherein the fresh cylinderoil has a TBN value of 80 or more.
 19. Process according to claim 1,wherein the fresh cylinder oil has a TBN value of 90 or more. 20.Process according to claim 1, wherein the fresh cylinder oil has a TBNvalue of 100 or more.